A circuit for providing a bias signal for a power amplifier includes a first input, a second input and an output. The first input is configured to receive an input signal to be amplified by the power amplifier. The second input is configured to receive the amplified input signal. The output is configured to provide the bias signal.
|
1. A circuit for providing a bias signal for a power amplifier, the circuit comprising:
a first input configured to receive an input signal comprising a digital baseband signal to be amplified by the power amplifier,
a second input configured to receive the amplified input signal,
an output configured to provide the bias signal;
a bias modifier configured to vary the bias signal for the power amplifier based on the input signal, wherein the bias modifier comprises a mapper configured to map the amplitude of the digital baseband signal to a digital voltage signal based on a predetermined relationship and a digital-to-analog converter (DAC) configured to convert the mapped digital voltage signal into the bias signal for the power amplifier;
a feedback receiver configured to determine an information describing the amplified input signal; and
an adjuster configured to adjust a distortion compensation rule based on the information describing the amplified input signal, which is provided by the feedback receiver, to counteract or compensate a distortion of the amplified input signal.
2. The circuit according to
3. The circuit according to
wherein the bias modifier is configured to perform an envelope tracking (ET) modulation,
wherein the feedback receiver and the adjuster are configured to perform an amplitude modulation (AM), and
wherein the adjuster is configured to adjust the distortion compensation rule to counteract or compensate a distortion of the amplified input signal induced by a time misalignment between the amplitude modulation (AM) and the envelope tracking (ET) modulation.
4. The circuit according to
a predistorter configured to perform a predistortion of the input signal to obtain a predistorted signal for the power amplifier,
wherein the adjuster is configured to adjust a predistortion rule, and
wherein the predistorter is configured to apply the predistortion rule to obtain the predistorted signal for the power amplifier.
5. The circuit according to
6. The circuit according to
7. The circuit according to
wherein the adjuster comprises a calculator configured to calculate correction values from the information describing the amplified input signal,
wherein the adjuster is configured to adjust the distortion compensation rule using the calculated correction values.
8. The circuit according to
wherein the feedback receiver is configured to determine an amplitude information (A) and/or a phase information (φ) describing the amplified input signal, and
wherein the calculator is configured to compare the amplitude information (A) and/or the phase information (φ) describing the amplified input signal and the amplitude information and/or the phase information describing a desired input signal and calculate the correction values on the basis of the amplitude information and/or the phase information comparison.
|
The present invention relates to a circuit, a transceiver and a mobile communication device. In particular, the present invention relates to a circuit for providing a bias signal for a power amplifier.
Recently, in order to save current in a transmit chain, the mobile phone manufacturers have been moving towards “envelope tracking”, which is a technique where the power amplifier is supplied through a fast DC/DC converter whose output voltage is varying over time as a function of the amplitude modulation. The concept of envelope tracking is to operate as close as possible to saturation during the modulation peaks and to lower the voltage when the instantaneous amplitude signal is low, thereby boosting the power amplifier efficiency.
However, there are significant challenges in this concept. In fact, the gain of the power amplifier is affected by the DC/DC voltage. Thus, if one simply tries to follow the peaks of the signal with the DC/DC converter, the gain variation will result in a distortion of the modulation.
Furthermore, AM/PM phenomena may take place, which will also impair the modulation quality, therefore resulting in spurious emissions (unwanted energy in neighboring channels) or an error vector magnitude (EVM) degradation.
In conventional systems there are two ways to minimize the unwanted phenomena highlighted above. One conventional approach is to choose the trajectory of the DC/DC control voltage accurately so that the power amplifier gain stays constant. It has to be noted, however, that as the signal level increases and the power amplifier approaches saturation, its instantaneous gain diminishes. In particular, the intention of envelope tracking is to increase the DC/DC voltage when the amplitude signal goes through a peak. Here, increasing the DC/DC voltage generally leads to a gain increase. By combining these two effects, a cancellation can be obtained; hence limiting the unwanted distortion of the signal. For this concept, the AM/PM phenomena introduced by the power amplifier should be negligible.
Another conventional approach is to compensate both AM/AM and AM/PM distortions by adequately predistorting the input wave into the power amplifier. This can be accomplished with an analog real-time closed loop architecture or using some fixed predistortion. The predistortion based on closed loop architectures typically requires extremely wide bandwidth in order to not create excess noise at a duplexer offset. When using the predistortion without the closed loop architecture, it is typically required that the characteristic of the power amplifier is known with good detail.
The first conventional approach of the envelope tracking relies heavily on the knowledge of the so-called “isogain” contours, which have to be individually calibrated on each phone. However, also the second conventional approach of the predistortion requires the knowledge of the AM/AM and the AM/PM curves as a function of the instantaneous DC/DC voltage.
A disadvantage of the first conventional approach is that calibrating the isogain contours is a long task, which prolongs the calibration time in the factory. Also, the calibrated isogain contours typically have to be stored in a random-access memory (RAM) and they are characterized in that they are fixed. This results in the fact that if the power amplifier characteristic is not perfectly stable over different conditions (e.g. aging, temperature, load, etc.), the matching of the gain loss because of a proximity to saturation and the gain expansion because of an increased DC/DC voltage can no longer be achieved, therefore leading to a spectrum worsening.
A disadvantage of the second conventional approach is that the AM/AM and AM/PM predistortion also requires a significant individual calibration. Furthermore, its adequateness is typically not always guaranteed under all circumstances.
Therefore, conventional systems are disadvantageous in that they are rather inflexible and in that a time-consuming calibration task in the factory is required.
The present invention relates to a circuit for providing a bias signal for a power amplifier. The circuit comprises a first input, a second input and an output for providing the bias signal. The first input is configured to receive an input signal to be amplified by the power amplifier. The second input is configured to receive the amplified input signal.
Furthermore, the present invention relates to a transceiver comprising a power amplifier, a bias modifier, a feedback receiver and an adjuster. The power amplifier is configured to provide an amplified input signal based on an RF input signal which is dependent on a digital baseband signal. The bias modifier is configured to vary a bias signal for the power amplifier based on the digital baseband signal. The feedback receiver is configured to determine an information describing the amplified input signal. The adjuster is configured to adjust a distortion compensation rule based on the information describing the amplified input signal, which is provided by the feedback receiver, to counteract or compensate a distortion of the amplified input signal.
Furthermore, the present invention relates to a mobile communication device comprising a digital baseband processor, a transceiver and an antenna port. The transceiver comprises a circuit and a power amplifier. The digital baseband processor is configured to provide a digital baseband signal. The circuit is configured to provide a bias signal for a power amplifier. The circuit comprises a first input, a second input and an output for providing the bias signal. The first input is configured to receive the digital baseband signal as an input signal to be amplified by the power amplifier. The second input is configured to receive the amplified input signal. The power amplifier is configured to provide the amplified input signal based on an RF input signal which is dependent on the digital baseband signal. The transceiver is coupled between the antenna port and the digital baseband processor.
The present invention will be subsequently described taking reference with the enclosed figures in which:
Before discussing the present invention in further detail using the drawings, it is pointed out that in the figures identical elements or elements having the same function or the same effect are provided with the same reference numerals so that the description of these elements and the functionality thereof illustrated in the different embodiments is mutually exchangeable or may be applied to one another in the different embodiments.
For example, the digital baseband processor 710 is configured to provide a digital baseband signal 715. In addition, the transceiver 720 may be configured to receive the digital baseband signal 715 as an input signal and to output an amplified input signal 725. For example, the antenna port 735 may be coupled to an antenna 730. In addition, the antenna 730 may be configured to relay (or transmit) the amplified input signal 725 provided by the power amplifier 150 of the transceiver 720.
In addition, the transceiver 720 may comprise a circuit 100 and a power amplifier 150. The power amplifier 150 may be configured to provide the amplified input signal 725 based on an RF input signal which is dependent on the digital baseband signal 715.
Furthermore, the circuit 100 of the transceiver 720 shown in
The mobile communication device 700 may be a portable mobile communication device.
As an example, the mobile communication device 700 can be configured to perform a voice and/or data communication (according to a mobile communication standard) with another (portable) communication device and or a mobile communication base station. Such a mobile communication device may be, for example, a mobile handset such as a mobile phone (cell phone), a smart phone, a tablet PC, a broadband modem, a notebook or a laptop, as well as a router, a switch, a repeater or a PC. Furthermore, such a mobile communication device may be a mobile communication base station.
The circuit 100 allows for an improved flexibility of the mobile communication device 700. For example, the circuit 100 can be used to counteract or compensate a distortion of the amplified input signal 725 in the mobile communication device 700.
Even though in
The conventional systems have the disadvantage that they are rather inflexible and that they require the time-consuming calibration task in the factory. Therefore, a need exists to provide an improved circuit avoiding this disadvantage.
Accordingly, it has been found that the just mentioned disadvantage can be avoided if a first input configured to receive an input signal to be amplified by the power amplifier, a second input configured to receive the amplified input signal and an output configured to provide a bias signal for the power amplifier are provided. Especially by providing the second input that receives the amplified input signal, it is possible to include an internal feedback receiver in the circuit or mobile communication device. Such an internal feedback receiver can be used instead of an external measurement device. By the use of the internal feedback receiver, it is possible to determine an information describing the amplified input signal on the basis of which a distortion compensation rule can be adjusted. This essentially provides an increased flexibility and avoids the time-consuming calibration task in the factory.
Furthermore, the circuit 100 may comprise the following additional features.
Referring to
Further referring to
For example, the adjuster 130 of the circuit 100 is configured to adjust the distortion compensation rule to counteract or compensate a distortion of the amplified input signal 725 induced by the bias signal variation.
Furthermore, the bias modifier 110 of the circuit 100 may be configured to perform an envelope tracking (ET) modulation. In addition, the feedback receiver 120 and the adjuster 130 may be configured to perform an amplitude modulation (AM). For example, the adjuster 130 is configured to adjust the distortion compensation rule to counteract or compensate a distortion of the amplified input signal 725 induced by a time misalignment between the amplitude modulation (AM) and the envelope tracking (ET) modulation. Here, it is pointed out that by counteracting or compensating the distortion of the amplified input signal 725 which is induced by the time misalignment between the amplitude modulation (AM) and the envelope tracking (ET) modulation, it is possible to provide a system (i.e. circuit 100, transceiver 720 or mobile communication device 700) that is able to avoid such time alignment problems.
Referring to
For example, the first input 102 of the circuit 100 is configured to receive a digital baseband signal 715 as the input signal 101. In addition, the bias modifier 110 of the circuit 100 may comprise a mapper 210 and a digital-to-analog converter 220 (DAC). For example, the mapper 210 is configured to map the amplitude of the digital baseband signal 715 to a digital voltage signal 215. Furthermore, the digital-to-analog converter 220 (DAC) may be configured to convert the mapped digital voltage signal 215 into the bias signal 115 for the power amplifier 150. The bias signal 115 (which is output by the circuit 100 shown in the example implementation of
Referring to
Further referring to
In the example implementation of
For example, the feedback receiver 120 is configured to determine the information 125 describing the amplified input signal 725 using a measurement signal 265 provided by a detector 260. As exemplarily depicted in
Furthermore, the detector 260 may be part of the feedback receiver 120 which is included in the circuit 100.
As exemplarily depicted in
According to
As already described before, the feedback receiver 120 may be configured to determine the amplitude information A and/or the phase information φ describing the amplified input signal 725. For example, the AM-AM/AM-PM calculator 230 is configured to compare the amplitude information A and/or the phase information φ describing the amplified input signal 725 and the amplitude information and/or the phase information describing a desired input signal 101, and calculate the correction values based on the amplitude information and/or the phase information comparison.
In
As opposed to the example implementation of
In the case of the predistortion according to
Summarizing
Referring to
The example table 500 of
For updating a predistortion coefficient by the predistorter 320 shown in
In the schematic diagram 600 of
Referring to
The transceiver 720 may further comprise a DC/DC converter 240 configured to adjust a supply voltage 245 of the power amplifier 150 based on the bias signal 115.
For example, the bias modifier 110 of the transceiver 720 is configured to generate an instantaneous bias signal 115 for the DC/DC converter 240. In addition, the bias modifier 110 and the DC/DC converter 240 may be configured to keep the gain of the power amplifier 150 constant.
Furthermore, the transceiver 720 may further comprise a detector 260 which is coupled to the output of the power amplifier 150. The detector 260 may be configured to provide a measurement signal 265 for the feedback receiver 120.
Furthermore, the adjuster 130 of the circuit 100 may be configured to update the distortion compensation rule in real time during the transmission of the mobile communication device 700.
In summary of the previous examples, it has been found that it is possible to use a feedback receiver for learning and updating isogain contours or predistortion coefficients, according to which approach is being used. It is noted here that the DC/DC converter can be driven with a function of the modulation and of the isogain contours.
Referring again to
For example, a feedback path can be used in order to ensure a closed loop power control. However, it has been found that the feedback is also able to monitor the quality of the output wave (which is a feature such as used in “U_APB” and predistortion algorithms).
An advantage of the present system is that it can be used to adjust the isogain curves. For example, the transceiver can monitor the AM/AM characteristic of the transmitter and determine whether the gain is constant over the dynamic range of the signal. From this curve, an expansion or compression can be monitored and this information will then be used to adjust the isogain contour (or the predistortion coefficients).
It may also be possible to make a slow learning without storing any coefficients. The system may start in the first slots with a high DCDC voltage and a low envelope tracking depth, therefore with a limited efficiency gain, but with linearity surely within limits. During the slot, linearity is observed and the transceiver can measure whether the proximity to saturation dominates (gain loss at modulation peaks) or the other way around (gain expansion at modulation peaks) and adjust the isogain contours accordingly. Then, the envelope tracking depth can be increased and this process is iterated. This process has been sketched with reference to
The example process of
In general, it has been found that it is possible to use an RF feedback to evaluate properties of the output wave in order to update envelope tracking coefficients and algorithms to update these coefficients in real time during transmission.
More specifically, an improved transmit system is provided which features a power amplifier and/or a transmit chain whose working point can be controlled by the transmit system, a fast DC/DC converter which is able to follow whole or part of the AM content, means to generate an instantaneous DCDC voltage, so that the gain of the power amplifier stays constant, a feedback path which is able to evaluate the quality of the output wave, an algorithm that optimizes the coefficients/tables and an algorithm that starts with a low envelope tracking depth and increases it during transmission.
The improved transmit system may also comprise sensors for sensing, for example, a temperature, a voltage and/or a current for enhancing the capabilities of the bias control algorithm.
Belitzer, Alexander, Sogl, Bernhard, Camuffo, Andrea
Patent | Priority | Assignee | Title |
11545945, | Mar 04 2020 | Qorvo US, Inc. | Apparatus and method for calibrating an envelope tracking lookup table |
11626844, | Mar 09 2020 | Qorvo US, Inc. | Envelope tracking radio frequency front-end circuit |
11671064, | Jan 07 2020 | Qorvo US, Inc. | Equalizer for envelope power supply circuitry |
11677365, | Jan 08 2020 | Qorvo US, Inc. | Envelope tracking power management apparatus incorporating multiple power amplifiers |
Patent | Priority | Assignee | Title |
5420536, | Mar 16 1993 | Victoria University of Technology | Linearized power amplifier |
20120106676, | |||
20130257529, |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Nov 09 2012 | CAMUFFO, ANDREA | Intel Mobile Communications GmbH | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 029541 | /0267 | |
Nov 09 2012 | BELITZER, ALEXANDER | Intel Mobile Communications GmbH | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 029541 | /0267 | |
Nov 09 2012 | SOGL, BERNHARD | Intel Mobile Communications GmbH | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 029541 | /0267 | |
Nov 12 2012 | INTEL DEUTSCHLAND GMBH | (assignment on the face of the patent) | / | |||
May 07 2015 | Intel Mobile Communications GmbH | INTEL DEUTSCHLAND GMBH | CHANGE OF NAME SEE DOCUMENT FOR DETAILS | 037057 | /0061 | |
Jul 08 2022 | INTEL DEUTSCHLAND GMBH | Intel Corporation | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 061356 | /0001 |
Date | Maintenance Fee Events |
Oct 21 2015 | ASPN: Payor Number Assigned. |
May 02 2019 | M1551: Payment of Maintenance Fee, 4th Year, Large Entity. |
May 03 2023 | M1552: Payment of Maintenance Fee, 8th Year, Large Entity. |
Date | Maintenance Schedule |
Nov 17 2018 | 4 years fee payment window open |
May 17 2019 | 6 months grace period start (w surcharge) |
Nov 17 2019 | patent expiry (for year 4) |
Nov 17 2021 | 2 years to revive unintentionally abandoned end. (for year 4) |
Nov 17 2022 | 8 years fee payment window open |
May 17 2023 | 6 months grace period start (w surcharge) |
Nov 17 2023 | patent expiry (for year 8) |
Nov 17 2025 | 2 years to revive unintentionally abandoned end. (for year 8) |
Nov 17 2026 | 12 years fee payment window open |
May 17 2027 | 6 months grace period start (w surcharge) |
Nov 17 2027 | patent expiry (for year 12) |
Nov 17 2029 | 2 years to revive unintentionally abandoned end. (for year 12) |